Left Ventricular Minute Work Index Research Articles

Effects of magnesium sulphate on the cardiovascular system, coronary circulation and myocardial metabolism in anaesthetized dogs

We have studied the effects of i.v. bolus doses of magnesium sulphate (MgSO4) 60, 90 and 120 mg kg-1 on haemodynamic state, the coronary circulation and myocardial metabolism in nine dogs anaesthetized with pentobarbitone and fentanyl. MgSO4 produced dose-dependent decreases in arterial pressure, heart rate, left ventricular dP/dtmax and left ventricular minute work index (LVMWI) and an increase in the time constant of left ventricular isovolumic relaxation. Stroke volume increased, systemic vascular resistance decreased and cardiac output did not change significantly. MgSO4 produced decreases in coronary perfusion pressure, coronary vascular resistance and myocardial oxygen consumption (MVO2). Coronary sinus blood flow, lactate extraction ratio and the ratio of LVMWI to myocardial MVO2, that is an index of cardiac efficiency, did not change significantly. This study indicated that the depressant effect of MgSO4 on cardiac function was offset by lowering of peripheral vascular resistance, so that cardiac pump function remained effective, and the almost constant coronary sinus blood flow resulted from the decrease in coronary vascular resistance even at higher doses.

Effects of graded infusion rates of propofol on cardiovascular haemodynamics, coronary circulation and myocardial metabolism in dogs

We have studied the effects of a 30-min infusion of propofol 6, 9, 12, 15, 18 and 21 mg kg-1 h-1 on cardiovascular haemodynamics, coronary circulation and myocardial metabolism in 12 mongrel dogs. Mean plasma concentrations of propofol after infusion of 6 and 21 mg kg-1 h-1 increased from 2.9 (SEM 0.3) to 11.5 (0.1) micrograms ml-1. Propofol produced a progressive decrease in arterial pressure. Heart rate tended to decrease at 15, 18 and 21 mg kg-1 h-1 and cardiac index decreased significantly at infusion rates > or = 9 mg kg-1 h-1. Systemic vascular resistance tended to increase except at 21 mg kg-1 h-1 and left ventricular systolic and diastolic function were depressed. Both coronary sinus blood flow and myocardial oxygen consumption decreased in parallel with a decrease in left ventricular minute work index without producing lactate. Propofol produced progressive decreases in coronary blood flow and myocardial oxygen consumption but did not exert adverse effects on the coronary circulation.

Effects of sevoflurane on cardiovascular dynamics, coronary circulation and myocardial metabolism in dogs.

The effects of 2.5% and 5% of sevoflurane anesthesia on hemodynamics and myocardial metabolism were studied in pentobarbital-pancuronium anesthetized dogs. The interaction between nicardipine and 2.5% sevoflurane was also examined. Sevoflurane produced dose-dependent ( P << 0.05 to P << 0.01) decreases in systolic arterial pressure (SAP), heart rate (HR), cardiac index (CI), left ventricular minute work index (LVMWI), maximum rate of rise of left ventricular pressure (LV dP/dt), the time constant of fall in isovolumic left ventricular pressure (T) and systemic vascular resistance (SVR), whereas stroke volume index (SVI) and left ventricular end-diastolic pressure (LVEDP) remained unchanged. Central venous pressure (CVP) was significantly ( P << 0.05) increased at 5%. Myocardial oxygen consumption (MV(O)(2)), and myocardial lactate extraction ratio (ML ext) were decreased in a dose-dependent manner ( P << 0.05). Myocardial oxygen extraction ratio (M(O)(2) ext) was significantly ( P << 0.01) decreased at 5%. The ratio of the left ventricular minute work index to myocardial oxygen consumption (LVMWI/MV(O)(2)), i.e., left ventricular efficiency was significantly decreased only at 5% ( P << 0.05). Coronary sinus blood flow (CSBF) was significantly ( P << 0.05) decreased only at 2.5% sevoflurane and coronary vascular resistance (CVR) was significantly ( P << 0.01) decreased only at 5% sevoflurane. The ratio of CSBF to CO (CSBF/CO) showed a tendency to increase as sevoflurane concentrations were increased. Nicardipine (0.01 mg.kg(-1)) administered intravenously under 2.5% sevoflurane caused significant ( P << 0.05 to P << 0.01) decreases in SAP, HR, LV dP/dt, SVR, and CVR, and increases in CVP, SVI, CI, and CSBF ( P << 0.05 to P << 0.01). CSBF/CO remained unchanged. MV(O)(2), M(O)(2) ext, and ML ext were significantly ( P << 0.05 to P << 0.01) decreased. LVMWI/MV(O)(2) showed a tendency to increase. It is concluded that sevoflurane causes a rapidly and easily controlled cardiovascular depression and may not have unfavorable effects on coronary circulation and myocardial metabolism. Nicardipine exerts a synergistic myocardial depressant effect on sevoflurane, in terms of both cardiovascular dynamics and myocardial metabolism.

Preoperative haemodynamic evaluation of patients submitted for renal artery stenosis.

The ECG, chest x-ray and haemodynamic parameters were investigated preoperatively in 19 patients subjected to surgery for renal artery stenosis (RAS) and in a control group comprising 19 normotensive patients subjected to other forms of major vascular surgery. Increased cardiac volume was demonstrated in 13 (68%) RAS patients and in two (11%) patients from the control group. Abnormal ECG (i.e. left ventricular hypertrophy or atrial fibrillation) was observed in 11 (58%) RAS patients and in one (5%) patient from the control group. In the RAS patients the following haemodynamic parameters were found to be statistically significantly increased, compared to the control group: systemic blood pressure, (systolic arterial pressure: +43%, diastolic arterial pressure: +38%, mean arterial pressure: +41%), pulmonary artery mean pressure (+64%), pulmonary capillary wedge pressure (+107%), heart rate (+15%), systemic vascular resistance (+27%), left ventricular minute work index (+46%) and right ventricular minute work index (+67%). The presence of increased cardiac volume and abnormal ECG were more closely related to the level of the pathologically increased pulmonary artery mean and wedge pressures than to the systemic blood pressure or central venous pressure. A preoperative haemodynamic evaluation is recommended to determine the degree of heart failure in RAS patients with: left ventricular hypertrophy and increased cardiac volume, or atrial fibrillation.

Hypertrophic nonobstructive cardiomyopathy: A precise assessment of hemodynamic characteristics and clinical implications

A precise assessment of left ventricular function was performed in 20 patients with hypertrophic nonobstructive cardiomyopathy to elucidate the basic pathophysiology and the data were compared with those In 22 normal subjects. Whereas end-diastolic pressure was high in those with cardiomyopathy, a more accurate Index of preload, end-diastolic stress, did not differ from normal value. Afterload was about half the normal value. Both isovolumic indexes [peak positive dP/dt and (dP/dt)/DP 40] and ejection phase indexes of contractility (ejection fraction) were in the normal range; however, the end-systolic stress volume ratio was significantly reduced (43% of the normal value). Although the left ventricular minute work index was in the normal range, the unit muscle performance (minute work/mass) was very low (49%). An abnormality of left ventricular relaxation was demonstrated by low peak negative dP/dt (56 %) and prolonged time constant T (191 %) and a stiff left ventricle was demonstrated by a high diastolic elastic stiffness constant (129%). These observations suggest that the contraction of a unit muscle is inappropriate to produce an adequate contraction of the whole ventricle and that hypertrophy might be an adaptive process to maintain normal systolic function by increasing mass and reducing afterload.

Cardiovascular effects of etomidate used for induction and in combination with fentanyl-pancuronium for maintenance of anaesthesia in patients with valvular heart disease.

The effects of induction of anaesthesia by etomidate 3 mg kg-1 followed by continuous infusion of etomidate 2 mg min-1, fentanyl 0.01 mg.kg-1 and pancuronium 0.1 mg.kg-1 were studied in ten patients with valvular heart disease. No haemodynamic changes were seen injection of etomidate, but after fentanyl was given there was a significant decline in cardiac index (10%), in mean arterial systemic pressure (20%), in systemic vascular resistance (14%), in left ventricular minute work index (27%) and in right ventricular minute work index (21%) compared to the control values. After supplementing with pancuronium, no further significant changes were seen. There was no significant change in the pulmonary vascular resistance during the whole study. In conclusion, it appears that etomidate is a safe intravenous agent, and is worth further study, in particular in patients with minimal cardiac reserve requiring high inspired oxygen tension.

Myocardial protection of only the left coronary artery perfusion in patients with isolated aortic valve replacement.

Effectiveness of only left coronary perfusion on myocardial protection was assessed by measuring serially cardiac functions such as cardiac index (CI), stroke index (SI), left ventricular minute work index (LVWI) and left ventricular stroke work index (LVSWI) in 22 consecutive patients with isolated, scheduled aortic valve replacement. The cardiac functions were determined 2,4 and 6 hours after open heart surgery. Correlation coefficients(r) between coronary perfusion time and the cardiac functions were less than 0.23, such being statistically insignificant. SI and LVSWI were in statistically significant inverse correlation to the preoperative NYHA classification and extracorporeal circulation(ECC) time for 4 hours following open heart surgery, and CI and LVWI for 2 hours. The correlation coefficients were highest at the 2nd postoperative hour and then decreased with passage of time. Therefore, the cardiac dysfunctions occurring in the postoperative period correlated either to the preoperative NYHA classification or ECC time, or both. It does, however, seem likely that the dysfunctions were correlated to ECC time as the recovery time of 4 hours from the dysfunction is too short for preoperatively existing dysfunction. Therefore, it was concluded that the continuous perfusion of only the left coronary artery was not the determinant factor of the postoperative dysfunctions and that the ECC time afforded detrimental effects, although such continued for 4 hours in terms of SI and LVSWI, and 2 hours in term of CI and LVWI.

Left ventricular function after repair of tetralogy of fallot and its relationship to age at surgery.

Left ventricular (LV) work-function curves were used to assess LV performance in eight postoperative tetralogy of Fallot (TOF) patients who underwent repair before 2 years of age (group 1) and 12 patients who underwent repair after 2 years of age (group 2). All patients were without significant residual shunts or pulmonary stenosis. Results were compared with those in seven control patients. Left- and right-heart hemodynamics were measured at various levels of afterload induced by methoxamine while heart rate was maintained constant. Cardiac output was serially measured. The slope (m) for each patient's LV end-diastolic pressure (EDP) vs LV minute-work index (MWI) relationship was determined. There were no significant differences in resting cardiac index, LV systolic pressure, LVEDP, aortic oxygen saturation or MWI among the groups. However, with afterload stress, group 2 patients had abnormal work-function curves with depressed slopes (m = 0.21 +/- 0.04) compared with the values for group 1 patients (m = 0.89 +/- 0.13, p less than 0.001) or the control group (m = 1.13 +/- 0.12, p less than 0.001). Thus, LV dysfunction unmasked by an afterload stress was present in the older TOF patients but not in the patients repaired during infancy. These findings raise the possibility that early, definitive repair of TOF may help preserve postoperative LV function.

Hemodynamic Effects of Nitrous Oxide Administered During Cardiac Catheterization

To assess the effects of nitrous oxide on hemodynamics and left ventricular function in man, 30 patients (24 of whom had coronary artery disease) were studied at the time of cardiac catheterization. Left ventricular peak-systolic pressure and end-diastolic volume showed no significant change during nitrous oxide inhalation. The maximum rate of pressure rise declined slightly, but left ventricular end-diastolic pressure and ejection fraction were unchanged. Heart rate and cardiac index declined modestly. The pressure-rate product and left ventricular minute work index decreased, suggesting a decline in myocardial oxygen requirements. These data suggest that nitrous oxide inhalation does not produce important depression of left ventricular performance. The consistent decrease in the determinants of myocardial oxygen demand suggests that use of this analgesic agent may be helpful in patients with coronary heart disease.

The cardiovascular effects of ketamine used for induction of anaesthesia in patients with valvular heart disease.

The effects of induction of anaesthesia by ketamine 2 mg.kg-1 were studied in six patients with valvular heart disease before tracheal intubation and operation. Cardiac index was unaffected because a mean decrease in stroke index was compensated for a mean increase in heart rate. A significant increase was found in mean arterial pressure, pulmonary arterial mean pressure, pulmonary capillary wedge pressure and central venous pressure. Systemic vascular resistance increased, but not significantly, whereas pulmonary vascular resistance increased significantly by more than 150 per cent. Right ventricular minute work index increased in all patients, and the increase was as much as 400 per cent. Left ventricular minute work index increased in four of the six patients, but the magnitude of the increase was not so marked. It is therefore concluded that ketamine causes pronounced pulmonary vasoconstriction and an undesirable strain on the myocardium. Such effects could prove deleterious in patients with limited functional reserve of the right ventricle.

Sodium Bicarbonate and Systemic Hemodynamics in Volunteers Anesthetized with Halothane

The cardiovascular effects of acute metabolic alkalosis (NaHCO3) in normal male volunteers anesthetized with halothane were measured. Pure metabolic alkalosis was studied by maintaning the end-tidal carbon dioxide tension at 40 torr. In each subject, cardiac index increased and total peripheral resistance decreased after each dose of NaHCO3. The increased cardiac index was associated with increased central blood volume, left ventricular minute work index, stroke index, and heart rate. Systolic time intervals showed increased myocardial performance. NaHCO3 administered to volunteers whose hearts were depressed by halothane appeared to cause peripheral vasodilation, volume expansion, and myocardial stimulation. The authors conclude that NaHCO3 administered during halothane anesthesia decreases total peripheral resistance and may lead to severe hypotension.

Cardiovascular responses to calcium administered intravenously to man during halothane anesthesia.

Calcium chloride (7 mg/kg) was administered intravenously to six healthy volunteers anesthetized with halothane. Cardiovascular changes were measured during constant ventilation and anesthetic depth under three conditions: 1) respiratory alkalosis, 2) normocarbia, and 3) respiratory acidosis. At each Paco2, calcium infusion significantly increased cardiac index, left ventricular minute work index, and stroke index. Heart rate, total peripheral resistance, and cardiac pre-ejection period decreased. No significant change in mean arterial blood pressure or central venous pressure followed calcium administration, and no arrhythmias occurred. It is concluded that calcium administration increases myocardial performance, presumably by increasing the availability of intracellular calcium ion for actomyosin interaction.

Hemodynamics and its regulation in old age

Experiments on adult and old rats and rabbits showed a decrease in the myocardial contractility with age. Cardiac output and stroke volume fall. Cardiac index and left ventricular minute work index decrease. The tension period phases and ejection period are prolonged. Diastole is somewhat shortened. The maximal rate of increase of the left ventricular pressure is declined. Contractility index, index of intensity of myocardial structures functioning, and systemic vascular resistance increase. Systemic arterial blood pressure does not show any essential changes. Excitability of vasoactive elements in various parts of brain shows a nonuniform changing. Their sensitivity to cathcholamines and acetylcholine increases. Extracardial nervous influences upon the heartare weakened with aging. Hemodynamic shifts in old animals occur after injection of smaller catecholamine and acetylcholine doses, as compared with adult ones. In old animals, smaller inderal and atropin doses block the corresponding β-adrenergic and cholinergic reactions. No age-related differences in the action of α-adrenergic blocker regitin were revealed. In old animals hemodynamic reflexes from the mechanoreceptors of the carotid sinus are decreased. The present investigation suggests that age-related shifts in the control of hemidynamics may play an important role in the circulatory changes occurring both under normal and pathological conditions in old age.

Myocardial function during atrial pacing in patients with angina pectoris and normal coronary arteriograms: Comparison with patients having significant coronary artery disease

Right atrial pacing at 140 beats/min for 8 minutes induced an electrocardiographic “ischemic pattern” in 10 patients with normal coronary arteriograms and chest pain usually typical of angina pectoris (group X). The findings were compared with those in 11 patients with demonstrable coronary arterial stenosis who had the same electrocardiographic “ischemic pattern” during pacing (group C). Six patients of group X and eight patients of group C experienced angina during pacing. In addition, a low level of myocardial extraction (less than 10 percent) or production of lactate was observed during pacing in five patients of group X and in seven of group C. Patients of group X showed a significant rise in cardiac index (P <0.05) and left ventricular minute work index (P <0.01), a significant reduction in left ventricular end-diastolic pressure (P <0.01) and unchanged systemic vascular resistance. In contrast, patients of group C showed a significant lowering of cardiac index (P <0.01), unchanged left ventricular minute work index and left ventricular end-diastolic pressure and increased systemic vascular resistance (P <0.001). “Pacing ventricular function curves,” obtained by plotting left ventricular stroke work index against left ventricular enddiastolic pressure, showed marked differences between the two groups. Although the clinical, electrocardiographic and metabolic manifestations were similar in both groups, the mechanism underlying these abnormalities is probably different. Indeed, if patients with the anginal syndrome and normal coronary arteries had myocardial ischemia, they should, like patients with coronary artery disease, exhibit a depressed or unchanged rather than enhanced left ventricular function during pacing stress. Right atrial pacing at 140 beats/min for 8 minutes induced an electrocardiographic “ischemic pattern” in 10 patients with normal coronary arteriograms and chest pain usually typical of angina pectoris (group X). The findings were compared with those in 11 patients with demonstrable coronary arterial stenosis who had the same electrocardiographic “ischemic pattern” during pacing (group C). Six patients of group X and eight patients of group C experienced angina during pacing. In addition, a low level of myocardial extraction (less than 10 percent) or production of lactate was observed during pacing in five patients of group X and in seven of group C. Patients of group X showed a significant rise in cardiac index (P <0.05) and left ventricular minute work index (P <0.01), a significant reduction in left ventricular end-diastolic pressure (P <0.01) and unchanged systemic vascular resistance. In contrast, patients of group C showed a significant lowering of cardiac index (P <0.01), unchanged left ventricular minute work index and left ventricular end-diastolic pressure and increased systemic vascular resistance (P <0.001). “Pacing ventricular function curves,” obtained by plotting left ventricular stroke work index against left ventricular enddiastolic pressure, showed marked differences between the two groups. Although the clinical, electrocardiographic and metabolic manifestations were similar in both groups, the mechanism underlying these abnormalities is probably different. Indeed, if patients with the anginal syndrome and normal coronary arteries had myocardial ischemia, they should, like patients with coronary artery disease, exhibit a depressed or unchanged rather than enhanced left ventricular function during pacing stress.

Hemodynamic Effects of Intravenous Digoxin in Acute Myocardial Infarction.

Meeting Abstracts1 May 1972Hemodynamic Effects of Intravenous Digoxin in Acute Myocardial Infarction.Harry Lipp, M.B.B.S., Pablo Denes, M.D., Miguel Gambetta, M.D., Leon Resnekov, M.D.Harry Lipp, M.B.B.S.Search for more papers by this author, Pablo Denes, M.D.Search for more papers by this author, Miguel Gambetta, M.D.Search for more papers by this author, Leon Resnekov, M.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-76-5-865_4 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptEight patients with acute myocardial infarction, three not in failure and five in moderate or severe clinical or hemodynamic failure, were investigated after the intravenous administration of 0.5 to 0.75 mg digoxin. Mean aortic pressure (Ao), mean pulmonary arterial pressure (PA), left ventricular filling pressure (LVFP), cardiac index (CI), stroke index (SI), arterial PO2, pulmonary arterial oxygen saturation (pulmonary arterial So2), systemic vascular resistance (SVR), left ventricular stroke work index (LVSWI), left ventricular minute work index (LVMWI), and tension time index (TTI) were obtained before and 1 hour after intravenous digoxin. Patients in moderate or severe failure had significant changes... This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAuthors: Harry Lipp, M.B.B.S.; Pablo Denes, M.D.; Miguel Gambetta, M.D.; Leon Resnekov, M.D.Affiliations: Chicago, Ill. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics 1 May 1972Volume 76, Issue 5Page: 865-866KeywordsAcute myocardial infarctionBlood pressureHemodynamicsOxygenPartial pressure of oxygenPulmonary arteryStrokeSystemic vascular resistance ePublished: 1 December 2008 Issue Published: 1 May 1972 PDF downloadLoading ...

The effect of atrial contraction on left ventricular performance in valvular aortic stenosis.

The instantaneous response of the left ventricle to loss or recovery of effective atrial contraction was studied in 12 patients with valvular aortic stenosis by producing A-V dissociation by electrical pacing of the ventricles so that some ventricular contractions were preceded by an effective atrial contraction while others were not. A conventional hydraulic formula relating size of the aortic valve orifice, pressure gradient, and flow was used to estimate beat to beat stroke volume. A properly timed atrial contraction augmented left ventricular performance in all patients, increasing stroke volume index from 14 to 55% (mean, 27%) and stroke work from 17 to 85% (mean, 45%). The contribution of atrial contraction to integrated cardiac performance was studied in six of the same patients by comparing cardiac performance with right atrial pacing and right ventricular pacing. With right atrial pacing, each ventricular contraction was preceded by an atrial contraction, while with right ventricular pacing many ventricular contractions were not preceded by atrial contraction. Right atrial pacing increased cardiac index in four of six patients: The mean increase for the total group was 13% and the mean increase in left ventricular minute work index was 17%. Although atrial contraction was capable of augmenting left ventricular performance in all patients studied, loss or recovery of effective atrial systole did not always alter integrated cardiac performance. Factors influencing atrial contribution remain poorly understood. Atrial contraction does not appear to have an unusual effect on the performance of the hypertrophied left ventricle.